Telephone system



. 1,5393 A. E. REINKE TELEPHOFE SYS TEN Filed Nov. 26, 1920HrThzzrEHez'zzke I Patented June 2, 1925.

UNETED STATES PATENT, OFFICE.

ARTHUR E. REINKE, OF HAGUE, NETHERLANDS, ASSIGNOR TO KELLOGG SWITCH-IBGARD AND SUPPLY COIVLPANY, OF CHICAGO, ILLINOIS, A CORPQRATION OFILLINOIS.

TELEPHONE SYSTEM.

Application filed November 26, 1920. Serial No. 426,366.

To (ZZZ 11:72am it may 00))067'71.

lie it known that I, ARTHUR E. REINKE, a citizen of the United States,and residing at The Hague, Netherlands, have inventedcertain new anduseful Improvements in Telephone Systen'is, of which the "following is adescription.

My invention relates to telephone systems and has to do moreparticularly with private branch exchange systems, such as are used forinterconnecting local subscribers terminating at a branch exchangeboard, and for also connecting local subscribers and main exchangesubscribers, and an object of my invention is the provision of animproved circuit arrangement which has desirable features of operation,all in a simple, eflicient' and economical manner In private branchexchange systems of the above type, it is desired to connect the branchexchange subscribers with main exchange subscribers, and in a board ofthis type it is often desirable to allow only certain ones of thesubstation lines terminating at the branch board to connect with themain exchange. One of the objects of restricting the service, of course,is to limit the use of the trunk lines strictly to business purposes,and so reduce the number of trunk lines require-d.

A feature of my invention is the provision of a plurality of jacks,which I term city service jacks, which are allotted to the lines at thebranch exchange in addition to the usual local 1acks for localconnect1ons. The

sleeve of the city servicejacks of the linesallowed city service areconnected to one pole or a battery. To the sleeve contact of each of thecity service jacks I connect a. conductor which leads to a sealed glasscabinet, which may preferably be placed where the person who has theauthority tor allotting the city service pri-vile-ges to the subscriberscan connect battery to the sleeves of any of the jacks that he desires.This feature of giving service to certain subscribers only may be calleddiscriminating service.

Another feature of my invention is the provision of a trunk circuit,used in. connecting a private exchange subscriber allowed city serviceto a main exchange subscriber, provided with means, responsive whenconnection is made with a city service ack, to extend the trunkconductors to the mam exchange. WVhen a connect1on is made with a jackof a subscribers line not allowed city service in an attempt to extend acon nection to the main exchange, the said means remains unoperated ornormal, and leaves the trunk conductors open to the main exchange sothat a connection is not extended to the main exchange.

The features as above outlined, as well as others, will be more fullyhereinafter described in the ensuing specification.

Referring now in general to my invention as illustrated in theaccompanying drawing, at A I illustrate a substation terminating at theprivate branch exchange switchboard in a local cut-oil jack LJ and aline signal S. At 0 I illustrate one of a plurality of branch exchangecord circuits with-which the board is equipped for interconnecting thebranch exchange subscribers, and which visory relay CS, the two relayscontrolling,

respectively, the answering supervisory and calling supervisory signalsAL and CL. A

listening key LK is provided for connecting the operators Set Oto thecord conductors,

and a ringing key RK is also provided which when actuated connectsringing current to the called line. SK which when actuated connects theringing key BK with a different source of ringing current. To the rightof the drawing I show a substation B similar to A and tel-mi natin-g atthe private branch exchange board in a local cut-off jack LJ and a.line: signal S.

The private branch exchange stations may be interconnected forconversational purposes by means of the cords C, and in addition certainof the local stations are allotted city service, whereby they may beextended to the main exchange and be connected to substationsterminating thereat. For this purpose, I provide jacks which I will termcity service jacks CJ, and the substations at the branch exchange thatare allowed city service are connected to the acks CJ. Each I also showa key of the subscribers lines may be connected to a city service jackCJ. In addition, I provide a terminal or connection box provided with aplurality of pairs of screw terminals T; the. screw terminals 50 of eachpair T. The COIIDGCHOII being connected to battery. box is provided witha suitable cover, which is sealed and can only be opened by an-awthorized person. The other terminals 51 of the pairs T are connected tothe sleeves of the-city service-jacks CJ Now, when a local substation isto be provided witha city service extension, a jackCJ is connectedto thesaid local substation (if not already provided. with a jack f CJ), inaddition to is regularlocal jack 'LJ and a jumper wire- 52 used toconnect the screw terminals 50 andf51, thus. extending the battery tothe, sleeve of the city service jack CJ; The local jack'LJ of thesubstation is connectedgto groundand the jack CJ isconnected-to bat teryfor purposes as will be more fully hereinafter described.

TWO-.Waytrunkcircuits TC are also pro-W vided in. additionto the localcords for connecting thesubstations provided with city service to themain exchange.

circuit as illustrated in the -.drawing termi' I nates at the privatebranclrexchange in" a trunk plug TR andiat the main exchange in alinecircuitL comprising the usual line. relay: LR,,cut-ofirelay-Co'andline signal The trunk circuit TC is provided with atrunkcordconductor control .relay TCR,I

which operates when the; plug TP 'is inserted intoa city service jack CJto extend the trunk cordconductors throughto the main exchange, butremains ,at normal when the said. plug TP. is inserted into a localjack.

LJ Orintoa. jackCJunot connected to bat- CA to inform the branchexchange, operator thatpa call is awaiting her attention from the vmainexchange. A listeningv key. LK"

and .aringing heylRK'f are provided 'for connecting, respectively, theoperators set i circuit through the calling supervisory lamp CL frombattery at normal contact 13 of the calling. supervisory frelay CS,-through the O and ringing. current fromgenerator G;

Aiswitching key CK is. also. provided for: nightcservice, as will bemorefully herein after described.

The-private branch exchange board is A providedwith a plu'rality oflocal cords LC,

and localjacks LJinto which the local substations :at the branchexchange terminate.

In addition .theibranch exchange board is ceiver, thus closing a circuitthrough the provided with city. service jacks CJ which are. allotted tothelocal substations for city extension service. A plurality of trunkcircuits TC are provided and are arranged in The trunk station-closes acirouitthrough linesignal S, traced from battery through the lamp S,normal contact 2 of the -jack*LJ, normal contact 3 of the city servicejack OJ, through the closed contacts at the substation switchhook, backthrough normal contact 4 of'jack CI to ground at normal contact -5 ofthe jack LJ. The lamp is lighted over-said'circuit, and the operatornoting the lighted 'signal inserts the answering plug AP of one oftheprivate branch exchange cords G into the jack 'LJ of thecallingsub'stationyand this insertion opens the contactsQ and 5 ofthejack L3 to eifaice the line-signal S; and establishes anenergizing-circuitfor the answering supervisoryrelay'AS;',-traced frombattery through the upper winding of relay AS; the tip contacts .0the'connected plug AP and jack LJ, through"--the-substation,"

back through the ring contacts of the connected plug APand jack'fLJ toground through the lower winding oi'relay AS.-

The-relay AS upon ,energization opens its normal contact 6 to preventthe lighting of the supervisorylamp ALat this-time. The" operator nowactuates'her listening keyLK' V to connect her operators set 0 to'thecord conductors of cord. C, the said set 0 being connected thereto overconductors 7 and 8,

normal contacts 9 and 10,'of the listeningkeys LK" of thetrunkcircuit'TG; and normal contacts.9 andlO' of a listening key ofanother trunk circuit, conductors 11 and 12,

the nowclosed contacts of the listening key LK'of the cord C- to thecord conductors.

The operator 'now inquires the wants of the callingsubstation, andassumingthat it is'the substation B' that is wanted,fthe operatorinserts the calling LJ of the wanted su station'B, and 'actuates theringing key RK to operate the call signal at the calletl station.The-insertion of the .plugCP into the jack Lil" closes a lamp CL, thesleeve-contact'ofthe plug GP The subscriber-at the substationB,-in'respouse .to his callsignal; removes hisrecalling-supervisory"relay CSat the now closed s'witchhook contacts atthe substation B, and the relay CS, upon energization,

plug GP into thejack opens its normal contact 13, thus effacing thesupervisory lamp CL, thus indicating to the operator that the subscriberat substation E has answered. The subscribers at the substations A and Bare now in conversational circuit, which may be traced over the heavilymarked conductors.

Upon termination of conversation, the subscriber at the callingsubstation A replaces his receiver upon the switchhook to open theenergizing circuit of the relay AS, and the relay restoring again closesits normal contact (3 to close a circuit through the supervisory lamp ALto ground at the sleeve of the jack LJ. The replacing of the receiver atthe substation B opens the energizing circuit of the supervisory relayCS and the relay restoring again closes it normal contact 13 to close acircuit through the supervisory lamp CL to ground at the sleeve of thejack LJ. The two lighted signals AL and CL indicate to the operator thatconversation has terminated, and she now withdraws the plugs AP and CPfrom their respective jacks LJ and LJ, thus effacing the said lamps, andthe apparatus used in establishing the above described connection is nowat normal and available for establishing other connections.

Assuming again that the subscriber at the substation A initiates a call,the said call is answered in the manner as above described, and theoperator now inquires the wants of the calling subscriber, and havingreceived a request from the said calling subscriber for a connection tothe main exchange, she will remove the plug AP from the local jack LJ.The subscriber at the substation A, as before mentioned, is providedwith city service and the substation A, in addition to its local jack LJat the branch exchange board, is provided with a second jack, which Iwill term a city service jack CJ, the, sleeve of the said local jack LJbeing connected to ground and the sleeve of the said city service jackCJ being connected to battery, and the purpose of the ground and batteryconnection for the respective jacks LJ and CU will be more fullyhereinafter described. The operator, after removing the answering plugAP of the local cord C "from the jack LJ, now inserts the trunk plug TPof the trunk circuit TC into the city service jack CJ of the callingsubstation A. The insertion of the plug TP into the jack CJ closes anenergizing circuit for the trunk control relay TCR, traced from batteryat the sleeve 14 of the jack CJ, sleeve contact 15 of the trunk plug TP,con ductor 16, through the winding of the relay TCR, conductor 17 toground at normal contact 18 of the control key CK. The insertion of theplug TP into the jack CJ also closes an energizing circuit for the supervisory relay SR, traced from battery through the lower winding of therelay SR, normal contacts ofthe ringing key RK, ring contacts of theplug TP and jack CJ, through the substation, back through the tipcontacts of the jack CJ and plug T]? to ground through the upper Windingof the relay SR. The relay SR upon energization closes its alternatecontact 19, establishing an energizing circuit for the supervisorycontrol relay CR, traced from battery at the sleeve 14 of the jack CJ,through sleeve 15 of the plug TP, normal contacts of the ringing key RK,over conductors 16 and 20, through the winding of relay CR, conductor21, normal contact 22 of the key CK and conductor 28 to ground atalternate contact 19 of relay SR. The relay CR upon energization closesits alternate contact 24, establishing a locking circuit for itselftraced from battery at the sleeve 14 of jack CJ, sleeve 15 of plug TP,conductors 16 and 20, through the winding of relay CR to ground at itsalternate contact 24. The relay CR and supervisory relay SR control thelighting of the supervisory lamp SS. The relay T CR upon energizationcloses its alternate contacts 25 and 26, closing the continuity of thetrunk circuit conductors and thus extending the line of the subscriber Ato the main exchange. The said trunk TC terminates at the main exchangein the line circuit L The closure of alternate contact 25 of the relayTCR bridges the resistance 27 across the trunk conductors to establishan energizing circuit forthe line relay LR of the line circuit L at themain exchange, traced from battery through the winding of relay LR,normal contact 28 of relay CO, resistance 27, conductor 29, alternatecontact 25 of the relay TCR, to ground at normal contact 30 of relay CO.The relay LR upon energization closes its alternate contact 30 to closea circuit through the line signal LS, which lamp LS is lighted to signalthe main exchange operator. The main exchange operator noting thelighted signal LS inserts the answering plug of a cord pair into thejack J and inquires the wants of the calling branch exchange subscriberat substation A and extends the call to the called line in the usualmanner. The resistance which is bridged across the trunk conductors uponthe energization of relay TCR places the supervisory signal of theanswering end of the main exchange cord under the control of the branchexchange operator. The called subscriber at the main exchange havinganswered in response to his call sigthe-usualdisconnect signal. :Thereplacing;

' of the receiver by the subscriberat the branch exchange substatiomAopens the energizing circuiti of the; supervisory relays SR at the:switchhook contacts, and' the; relay SR 5 upon restoration 1 closes itsnormal: -con i tact 19;"establishing .an energizing circuit for thesupervisory lamp SS, tr-aced-fromw battery at alternate contactifill o'tthe relay. CR, through the lamp SS, conductor 32; to ground atwnormal'contact- 19 of the supervisory relay SR The lighting of theisupervisorysignal SS indicates tothe branch exchange -operator that the subscriberat substation A has replacedihis receiver upon the switchhook, and shenow Withdraws the plug TP from theack CJ opening the energizingcircuits-of the relays TOR and CR.- ThereIay-CR in restoring opens itsalternate contact 31, el'l'acmg the supervisory signal SS, andtherelay'lCR in restoring opens;

ing the main exchange operator a disconnect signaland she now Withdrawsthe plug frorn the andthe apparatus used in establishing theconnectionis now at normal and available for establishing :otherconnections.

Assuming that the subscriber A to whom city service is allottedreceiv'esa call from the main exchange the voperator at I the said main exchangelnserts the calllng plugof a cord pair in the jack J which is associatedwith the-trunk cord TC and'projects ringing current-to the branchexchange. The

current extendsfrom the tip of'the jack- J through alternate contactofrelay 'CO,

condenser--3 l,-through the lower Winding r of relay RR,-over=conductor36, normalcontact 26 of relay T CR, alternate contact 28.- of relay COto the sleeve of the jack J. The

ringing current passing through thcuwindf ing 35 0f: relay RR causestheenergization ofthe relay RR, andthe closure of itsalter nate contact'87 establishes a lockinglcircuit for itself through its lockingWinding, traced from batteryat normal contact 38' of relay TCR, throughwinding 39 of relay: HR to ground I at alternate contact 37 of relayRR." The closingof-alternate contact 37 of relay RR also-establishes-acircuitfor the call lamp CA, 't1'aced-:from battery through the saidlamp CA and through alternate contact 37 to ground. The lamp CA islighted and notifies the operator that a call from theniain exchange isawaiting: her attention. The private branch exchange I operatornotingthe lighted signal actuates the listening key LK ot the trunk cord TCand receivesthe' number-or name of the subscriber wanted at the branchexchange. The

m-aining lighted until the subscriber A closing-of alternate contact ofthe listening key LK bridges the resistance 27 across 1 a the trunk-icord conductors to" operate the supervisory signalat the main exchangeso asto notify-the mam exchange operator that the call has been answeredby the branch 'exchangeoperaton, Assuming that it is the subscriber Athat is wanted, the branch ex- Clla-Dg8 OPEllltflIFlIlSBlliSitllG trunkplug Tl into the jack CJ of; the wanted line to close arr-energizingcircuit..for the relay TCR," traced from battery at the sleeve 14 ofthe" .jack OJ, over sleeve lolofthe plugTP, conductorn 16 through thewinding of relay 7 TCR conductor 17," to ground at normal contact 18 ofkey'CK. The .relay'TCR,

upon energization', closes itsialternate contact 41, establishing anenergizing circuit. for the supervisory-{lamps SS, traced .rmm

battery at. alternate contact 41, over conductors 42 and .43,normalcontact 31'of relay -CR,itl1I'OllglLtll8 lamp ZSS and overconductor32 to ground at normal contact 19 of supervisory relay SE -thesaid lamp reanswers.

The relay {FOR upon energization opens itsn01mal'c0ntact38 to open thelocking circuit of the winding 39 of the relayRR,

and the relay RR now restores and opens its alternate contact 37 toeflace "the signal CA. The. closingof alternate contacts 25 and 26 ofrelay TCR extends the trunk conductors through to-the substation Alandthe closing of alternate contact 25 maiintains-the resistance 27. acrossthettrunk conductors for controllingitlie supervisory signal at. themain exchange, after tlietoperator of-the branch exchange; has restoredher listening key- LK ator now actuatesthe: ringing key BK oftllButIllIllQ cord- TO to connect ringing cur-" rent over a pathextending from one pole of the: generator Grover conductor 44,throughalternate contactwof'the ringing xkey BK, ringicontacts oftheplug'iTPi and jack OJ, through the call bell andacondenser atthe' calledstation A,baok through the tip contacts ofthe connected jack CJ J andplug T'P, 1 thenother alternate contact ofthe ringing k'ey RKandconductor 45 to the other pole of the genera-tor. Thei subscriber-i inre sponseto hiscztllsignabremoves his receiver from the switchhook'i andcloses an "energizingw circuit for ithel supervisory relay SR. The saidrelay. SR; .upon energization, closes its alternate contact 19 to closean energizing' circuit;- for the relay i CR. tracedi from ground-atalternate contact 19 of relay SR," over iconductor 23 normal cont act 22of key CKwconductor 21,.the winding ct relayCR, conductors 20 and 16,sleeve 15 ot plug TP, to battery atsleeve-M of jack- CJ. The relay ORupon enengization closes" a locking circuit foritself, traced fronrbat-The privatebranch exchange oper- .1

tery at sleeve 14 of jack OJ, over conductors 16 and 20, through relayOR to ground at its alternate contact 24. The opening of normal contact19 of the relay SR e'ffaces the supervisory signal SS, thus notifyingthe branch exchange operator that the sub scriber at A has answered. Thesubscribers are now connected in conversational circuit, and the talkingcircuit may be traced over the heavily marked conductors.

The subscribers having finished conversation, they replace theirreceivers upon their respective switchhooks, and the replacing 01: thereceiver at the calling substation in the main exchange gives the mainexchange operator the usual disconnect signal, as is well understood.The replacing of the receiver at the called station A at the privatebranch exchange opens the energizing circuit of the supervisory relay SRat the switchhook contacts, and the closing of normal contact 19 ofrelay SR closes a circuit through the supervisory lamp SS, traced frombattery at alternate contact 31 of the relay. OR, through the lamp SS,and conductor 32 to ground at normal contact 19 of the supervisory relaySR. The lamp SS is light-ed over this circuit and indicates to thebranch exchange operator that the subscriber A thereat has replaced hisreceiver and conversation has terminated. The operator then withdrawsthe trunk plug TP from the jack OJ of the called line A. The withdrawalof the plug T]? from the jack OJ opens the energizing circuit of therelays OR and TOR. The relay OR upon restoration opens the circuit ofthe signal SS, and the de-energization of relay TOR opens the bridgeincluding the resistance 27 across the trunk conductors. The opening ofthis bridge brings about the lighting of the supervisory signal at themain exchange, and the operator noting the lighted signals withdraws theplug from the jack J. The apparatus used in establishing the abovedescribed connection is now at normal and available for establishingother connections.

Should the subscriber at the substation A, who is provided with a cityservice jack OJ, desire to remain in direct connection with the mainexchange for the purpose of establishing several city connections, theoperator 0 t the branch exchange after having inserted the plug TP intothe jack OJ, actuates the control key OK, and this opens the initialenergizing circuit of the relay TOR at the normal contact 18 of the keyOK, but a substitute circuit is established for the relay TOR, tracedfrom battery at the sleeve 14 of the jack OJ. through sleeve contact 15of the plug TP, conductor 16, through the winding of relay TOR,conductor 17, alternate contact 18 of key OK, conductor 23 to ground atalternate contact 19 of the supervisory relay SR. The resistance 27 isopening and closing of contact 19 of relay I SR brings about thede-energizationand energization of relay TOR, which relay TOR opens andcloses the bridge 27 across the trunk conductors and causes the flashingof the supervisory signal at the main exchange.

Should the private branch'exch-ange operator by chance, orintentionally, insert the plug TP of the trunk TO into a local jack LJof the line, no energizing circuit for the relay TOR of the trunkcircuit TO is established, as the sleeve of the jack of the local jackLJ is connected to ground and the other terminal of the relay TORisconnected to ground. Should the branch exchange operator insert the plugTP into a local jack LJ, and then actuate the key OK, and should thesubscriber at the substation that terminates in the jack LJ intowhichthe plug TP has been inserted, have his receiver off the hook, noenergizing circuit for relay TOR is established, as the circuit throughrelay TOR under these conditions extends from ground at the sleeve ofthe jack LJ to ground at alternate contact 19 of the relay SR, throughthe alternate contact 18 of the key OK, and the relay TOR failing toenergize, the connection is not extended to the main ex- 100 change.

Should the operator of the branch exchange insert the plug TP into alocal jack LJ from which the ground has been maliciously removed, andthen place the sleeve of either plug AP or OP to the sleeve of theinserted trunk plug TP, no operative energizing circuit is establishedfor the relay TOR, of the trunk circuit TO, as the said relay TOR isadjusted to operate from 24 volts direct, but will not operate in serieswith a supervisory lamp as AL or OL.

Should the operator at the branch ex change insert an answering plug APof a local cord into the local jack of a line and actuate the listeningkey LK of the cord O and the listening keys LIC of two trunk circuitsTO, no connection will be established as the circuit over conductors 11and 12 leading from the alternate contacts of the listening key LK willbe disconnected at the normal contacts 9 and 10 of the listening key LKand at normal contacts 9 and 10 of one of the listening keys of anothertrunk circuit TO, which was actuated. From-the above it may be seen thatthe blocking of an illegal connection is positive, and to receive cityservice the local substation, in addition to the local jack for localconnections, must be provided with a city service jack at OJ connectedto battery. *Shouldthe operator plug into a-i ack'CJ; notconnected-togbattery,

, the relay-PCB cannot: be operated.

*Fornightservice so that a'private branch exchange "subscriber can makeoutgoingcalls, the plug "PP is placed-in a jack CJ and keys and CKoperated. The operation of prevents thelfighting of lamp -SSWh8n thereceiver "at "the calling substation is on the sWitchhookJ'No current isusedrbyany of the relays at the'branch'exchange when the trunk circuitis -*e'om1e'ct'ed to a subscribers' {line jfor' nightservice, i the keysGKI and CK" operated, and the receiver at the subst a- VhiIe lhayevdesorrbed a specific form of {ny' nvention, I do not,'honever,-wish to he imitedto the exact circuitarrangement as tion on'fits'switchhooli.

I illustrated and described, as changes and modifications -will' readilysuggest theinselves iby" those skil=ld lnith6= w31t,:.fllld I,=therefore,"aim to'coverall such changes and modifications as comeWithin the spirit and scgge jof the appended claims. 3 hat'I'c'lahnas-new and desire-to secure oyUnited states Letters Patent, is

1 .lL g A manually operated telephone system including a number oftelephone 1 lines of difiiefeht cl'a'sses; 'exten'ding fromsubstationsto terminals at an-"exchange switchboard; a ;comrn'on battery terminal 5block for supplying potentiaitothe terminals ofonesof said "classes, a"-eonnecting;ieircuitfon usc.in=extelephone lines extending fromsubstations to an exchange switchboard, terminals for saiditelephonelines, conductors extending fromthe' terminalsto a terminalablock,oonnectingi circuits"' 1 for extending connections from saidtelephoneglines to a distant: ex-- change, means iotapplyingzpotentialto certain of th'e conductorsextendingito said terminal block, and meansin said connecting circuit 'operati've when: the sai d: connectingcircuit-is connected toone ofsaid lines:to

,v hijch a potential is connected to .extenddihe said line; throughtothe distant exchange, said last} means being iITOPBI zttIVBfWlIQD saidconnecting c rcu t is conneot-edto one of said lines to which "n05potential hasubeen. connecte 3: Aetelephone "system iliclliding 'i sub-.sqribei's linesextending from A substations and-terminating in'connection terminals-at an exchange switchboard, said connectionttl'llllllfllflbeillg provided with test contact some i of, whichhavebattery. potential cor.- nected thereto, while others haveground-potential connected thereto, aconneoting circuit for extendingconnections from said lines toa distant exchange, via certaiirot saidconnection terminals, discrin ii-nating means ;in said connecting(ZlIECIlitOPQIZIlJlYG when connected to oneofisaid lines through one setsaid termina'ls having a-battery :potentialconnected to thei-testcontact for connecting the K line through to the distant .exchange, said-.disorimi-nating means not. beingioperable When-the 'connecting'circuitis connected to oneof-saidili-nes through asterminal having agmnndipotentialconnected to the itest I contact; thereby. preventing theconnection :ofisa-idulast .line. to the distant ,"ex-

change,andinieans foripilacingsaiddiscriminating meansmnder the control.of the con nected -si ibscriber' when the ieonnecting-cir- .cuitis'connectedto a terminallha'ving-bat tery potential on i its testcontact.

1 4. A1 manually ii'operatedrtelephone exchange system iha'vingi linesof different chraraetersextending dimm S stations. to an exchangeswitchboard, adink' circuit -t'ior use in extendi-ng connections.--inom.-.said lines to a distant exchange, normally .open con ct in theconductors -ot said dink circuit, abattery, abridged across saidilinkncirrouit rat .the

distant exchange; signaling means .included in said bridge,discriminating-means inisaid dink: circuit.- wherebyi ywhenaaaidglinkcircuit is connected to a li-neof; one character. said discrimmating:means operates: to .place: a bridge across thevlink circuit toiopeizatesaid signaling means :at the distant exchange and to closesaith-normally opencontacts, .Wllllll when i said link. circuit isconnected it o. a line of adifllerent character saiddiscriminating meansdoes-not operate to iclose, a bridge across the link circuit cooperatethe sign-a ling means atithe. distant exchange andineans for placingsaid discriminating, means. .nnder the control zof-ithe connected-1subscriber when said link eireuitzisconnectedto a line of =saidlonecharacter.

5. A telepli.(me .-exchange. system; having lines of diflierentcharacters extending .ti'ion'i substations l to i :a n exchangeswitchboard, a1

cuit, anbattery bridged across. saidqlink ,cir

c-uit atji the distant .--excl1ange, signaling means ,included in.saidbridgca discriininatingineansiin saidlink cimuit whereby whensaidilink circuit is'conn ed to a lineof one charactersaith-discriminating means opcrates to. place. a, bridge acrossthe linkcircuit to operate-nsaid signaling, means at the .dis-

,tant; exchange and: to close said normally open con acts, while whensaid link circuit means is connected to a line of a different charactersaid discriminating means does not operate to close a bridge across thelink circuit to operate the signaling means at the distant exchange,said discriminating means being operable when a call is extended fromthe distant exchange to a subscriber at the exchange switchboard ot thefirst of said classes for connecting the said subscriber with thedistant exchange and being inoperative when extending a call to asubscriber of the other of said classes for connecting the saidsubscriber to the distant exchange, a supervisory signal at the distantexchange controlled by said discriminating means, and for placing saiddiscriminating means under the control of the connected subscriber whensaid link circuit is connected to a line of said one character wherebythe operator at the distant exchange may be signalled from the connectedsubscribers substation.

6. A telephone system including subscribers telephone lines extendingfrom substa tions to an exchange switchboard, a link circuit forextending connections from said substations to a distant exchange, anormally open contacts in the conductors of said link circuit, asupervisory signal for said link circuit operable by a subscriber whenthe link circuit is connected to one of said subscribers lines,responsive to the opening and closing of the bridge across thesubscribers lines, a signal for said link circuit at the distantexchange and means in said link circuit for closing said normally opencontacts and also for rendering the signal in the link circuit at theexchange switchboard inoperative responsive to the opening and closingof the said bridge across the subscribefls line and for rendering saidsignal at the distant exchange operable by the opening and closing ofthe bridge across the subscribers line.

7. A telephone system including subscribers lines extending fromsubstations to an exchange switchboard, a connecting circuit having itstalking strands normally in open circuit, means for closing said talkingstrands to extend calls from said subscribers lines to a distantexchange, a signal for said connecting circuit at the exchangeswitchboard and a second signal at the disant exchange, means controlledover a connected subscribers line for operating the signal at theexchange switchboard but not the signal at the distant exchange, andmeans for preventing the operation of the signal at the exchangeswitchboard and for rendering operative the signal at the distantexchange.

8. A telephone system including subscribers lines of differentcharacters extending from substations to an exchange switchboard, aconnecting circuit having its talking conductors normally in opencircuit for ext-ending calls from said subscribers lines of onecharacter to a distant exchange, discriminating means for saidconnecting circuit for preventing the subscribers lines of anothercharacter from being extended to a distant exchange, a signal for saidconnecting circuit at the exchange switchboard, a second signal at thedistant exchange under the control of said discriminating means, meanscontrolled over a connected subscribers line for operating the signal atthe exchange switchboard but not the signal at the distant exchange,means for said link circuit including a switchboard operators manuallyoperated key for placing said discriminating means under the control ofthe connected subscriber for rendering the signal at the distantexchange responsive to the substation control and the said first signalat the exchange non-responsive to the substation control, and a thirdsignal for said connecting circuit at the exchange switchboardcontrolled from said distant exchange for indicating a call from saiddistant exchange.

9. A telephone system including subscribers lines extending fromsubstations to an exchange switchboard, a connecting circuit forextending calls from said subscribers lines to a distant exchange,normally open contacts in the talking conductors of said connectingcircuit, automatic means for closing said normally open contacts, asignal for said connecting circuit at the exchange switchboard and asecond signal at the distant exchange, means controlled over a connectedsubscribers line for operating the signal at the exchange switchboardbut not the signal at the distant exchange, and means for rendering thesignal at the exchange switchboard non-responsive to the substationcontrol and for rendering the signal at the distant exchange responsiveto the subscriber control.

10. A telephone system including subscribers telephone lines extendingfrom substations to an exchange switchboard, a link circuit for use inextending connections from said substations toa distant exchange, meansin said link circuit for opening and closing the talking strands of saidlink circuit, means responsive to the connection of said link circuit toone of said subscribers lines for operating said means to close theconductors of said link circuit, and locking means for preventing theconnected sub: scriber from opening the conductors of said link circuit.

11. A telephone system including subscribers telephone lines extendingfrom substations to an exchange switchboard, a link circuit for use inextending connections from said substations to a distant exchange, meansin said link circuit for opening and closing the talking strands of saidlink circuit,

means responsive to the connection of said 7 link circuit to one of saidsubscribers" lines for operating sa'id means to close the conductors ofsaid link circuitylocking means for preventing the -connected subscriberfrom opening the conductors of said link circuit, and means in saidllink'circuit' for rendering signaling means atthe distant'exehange.

Signed by me at The Hagueg the Netherlands, this 5th day of November,1920.

ARTHUR E: REINKE.

